A 5G optical module three - order HDI high - speed PCB process

Abstract

The present invention discloses a 5G optical module three - order HDI high - speed PCB process, which includes: there are at least 8 layers arranged from top to bottom in the PCB, namely L1, L2, L3, L4, L5, L6, L7, L8 in sequence. The L3 and the L6 are signal layers. One core board is arranged between the L2 and the L3 and forms a first double - sided core board, and another core board is arranged between the L6 and the L7 and forms a second double - sided core board; Process flow: S010, the first double - sided core board and the second double - sided core board are pre - drilled with laser blind holes, copper - plated, and electroplated to fill the holes; S020, the L1, the first double - sided core board, and the L4 are pressed into a first four - layer board, and the L5, the second double - sided core board, and the L8 are pressed into a second four - layer board; S030, the first four - layer board and the second four - layer board are pressed into an eight - layer board; It realizes the improvement of the dielectric thickness consistency, signal transmission stability, and the arbitrary conduction of stacked holes in multi - layer HDI.

Description

Technical Field

[0001] The present invention relates to the field of network communication optical module technology equipment, and in particular to a 5G optical module three-order HDI high-speed PCB process. Background Art

[0002] The network communication optical module realizes the photoelectric / photoelectric conversion. The sending end converts the electrical signal into an optical signal, which is transmitted through optical fiber, and the receiving end converts the optical signal into an electrical signal. Without the optical module, there is no "network". The current 5G network has a large bandwidth requirement, with a rate from 25GB / s-100GB / s (fronthaul) and from 25GB / s-400GBGB / s (backhaul), which puts forward higher bandwidth and more scenarios requirements for the bearer network, especially the optical module.

[0003] like Figure 1 As shown, the traditional manufacturing method uses the L4 / L5 layer as the inner core board before the first lamination, first presses it into a 4-layer board, performs laser drilling of blind holes, electroplating to fill the holes, and then performs three laminations, laser drilling of blind holes, mechanical drilling of through holes, and copper plating in sequence to achieve interconnection of any layer of the 8-layer board.

[0004] This traditional technical method only realizes the interconnection of 8-layer boards. Through multiple sample tests, the signal rate does not meet the standard. The main influencing points of the impedance signal are: dielectric layer thickness and line width (the dielectric constant of the material here depends on the material itself, which is the PCB manufacturing process). The reason is that the signal layer of this PCB product is L3 and L6. The transmission rate of the signal layer mainly depends on the consistency of the dielectric layer thickness between L2 / L3 and L5 / L6, as well as the line width consistency of these two layers. In the traditional manufacturing method, the dielectric layer thickness between L2 / L3 and L5 / L6 is corresponding to the thickness of the dielectric layer. After the L3 and L6 layers are formed into lines, the semi-cured sheet is used to fill the line gap and bond and solidify. The line copper has a thickness of 20-30um. When the semi-cured sheet fills the line layer thickness and line gap, the glue flow and filling are large, and the thickness fluctuation of the formed dielectric layer is increased and the consistency is insufficient. The thickness tolerance of the dielectric layer formed by this traditional method will reach ±0.075mm, which has poor signal transmission stability.

[0005] like Figure 2 As shown, for the signal layers L3 and L6, the traditional process is to perform secondary pressing after circuit etching, and rely on semi-cured sheets for high temperature and high pressure curing. In this method, after the semi-cured sheet (the dielectric layer indicated by the four arrows) is dissolved at high temperature, it is necessary to fill the gaps between the lines after etching the L3 and L6 layers. The amount of filling affects the fluctuation of the thickness of the dielectric layer, and the thickness uniformity of the dielectric layer is poor, which leads to the stability of high-frequency and high-speed impedance signal transmission of the L3 and L6 layers.

[0006] Therefore, there is an urgent need for a 5G optical module third-order HDI high-speed PCB process that can solve one or more of the above problems. Summary of the Invention

[0007] To solve one or more problems existing in the prior art, the present invention provides a 5G optical module third-order HDI high-speed PCB process. The technical solution adopted by the present invention to solve the above problems is: a 5G optical module third-order HDI high-speed PCB process, which includes: the signal layer is laminated with copper foils on both sides of a prepreg to form a double-sided board;

[0008] There are at least 8 layers in the PCB arranged from top to bottom in sequence, namely L1, L2, L3, L4, L5, L6, L7, L8. The L3 and the L6 are signal layers. A core board is arranged between the L2 and the L3 and forms a first double-sided core board, and another core board is arranged between the L6 and the L7 and forms a second double-sided core board;

[0009] Process flow: S010, the first double-sided core board and the second double-sided core board are pre-laser drilled with blind holes, copper deposited, and electroplated to fill the holes;

[0010] S020, laminate the L1, the first double-sided core board, and the L4 to form a first four-layer board, and laminate the L5, the second double-sided core board, and the L8 to form a second four-layer board;

[0011] S030, laminate the first four-layer board and the second four-layer board to form an eight-layer board.

[0012] Further, it also includes: S021, after the first double-sided core board is cut, it is sequentially subjected to brownification, laser drilling of blind holes, copper deposition, electroplating to fill the holes, circuit pattern, circuit etching, optical inspection, laminating the L1, the first double-sided core board, and the L4 to form the first four-layer board, performing circuit pattern on the first four-layer board, performing circuit etching on the first four-layer board, and performing optical inspection on the first four-layer board;

[0013] S022, after the second double-sided core board is cut, it is sequentially subjected to brownification, laser drilling of blind holes, copper deposition, electroplating to fill the holes, circuit pattern, circuit etching, optical inspection, laminating the L5, the second double-sided core board, and the L8 to form the second four-layer board, performing circuit pattern on the second four-layer board, performing circuit etching on the second four-layer board, and performing optical inspection on the second four-layer board.

[0014] Further, it also includes: S040, performing laser drilling of blind holes, copper deposition, and electroplating to fill the holes on the eight-layer board.

[0015] Further, it also includes: S041, performing laser drilling of blind holes, mechanical drilling of through holes, copper deposition, and electroplating to fill the holes on the eight-layer board.

[0016] Further, it also includes: S042, after electroplating the vias, the eight-layer board is successively subjected to circuit pattern, circuit etching, optical inspection, solder mask characters, lead electroplating with gold, forming, electrical testing, appearance inspection, and packaging.

[0017] The beneficial value obtained by the present invention is as follows: In the present invention, the signal layer is formed by laminating copper foils on both sides of a prepreg to form a double-sided board, so that the prepreg does not need to fill the gaps between the etched circuits with glue, achieving high consistency in dielectric thickness. Furthermore, it ensures the stability of high-frequency and high-speed impedance signal transmission in the signal layer, and solves the problem of the influence of the thickness uniformity of the dielectric layer caused by the filling of prepreg after etching. Then, the PCB is produced and processed according to the above process flow. Compared with the traditional process flow, it reduces one lamination process, reduces the influence of high temperature and high pressure on the expansion and contraction of the PCB board material, is of great help to improving the alignment accuracy of stacked vias, and realizes the conduction of third-order HDI stacked vias through this process flow, and further realizes the arbitrary conduction of stacked vias in multi-layer HDI. The above greatly improves the practical value of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram I of the design and manufacturing method of traditional 8-layer third-order HDI PCB stacked vias;

[0019] Figure 2 It is a schematic diagram II of the design and manufacturing method of traditional 8-layer third-order HDI PCB stacked vias;

[0020] Figure 3 It is a schematic block diagram of the process flow of the present invention;

[0021] Figure 4 It is a schematic diagram of the layer board design of the present invention;

[0022] Figure 5 It is a schematic diagram of the layer board design and stacked via design of the present invention;

[0023] Figure 6 It is a schematic diagram I of the finished PCB effect of the present invention;

[0024] Figure 7 It is a schematic diagram II of the finished PCB effect of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] To make the above objects, features, and advantages of the present invention more understandable, the following will describe the specific embodiments of the present invention in detail with reference to the accompanying drawings. Many specific details are set forth in the following description to facilitate a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from this description, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0026] As Figures 3 - 5 shown, the present invention discloses a 5G optical module three - order HDI high - speed PCB process, which includes: the signal layer uses prepreg to attach copper foils on both sides and is pressed into a double - sided board;

[0027] There are at least 8 layers arranged from top to bottom in the PCB, namely L1, L2, L3, L4, L5, L6, L7, L8. The L3 and the L6 are signal layers. A core board is arranged between the L2 and the L3 and forms a first double - sided core board, and another core board is arranged between the L6 and the L7 and forms a second double - sided core board;

[0028] Process flow: S010, the first double - sided core board and the second double - sided core board are pre - drilled with laser blind holes, copper - plated, and electroplated to fill the holes;

[0029] S020, press the L1, the first double - sided core board, and the L4 into a first four - layer board, and press the L5, the second double - sided core board, and the L8 into a second four - layer board;

[0030] S021, after the first double - sided core board is cut, it is sequentially browned, drilled with laser blind holes, copper - plated, electroplated to fill the holes, circuit pattern formed, circuit etched, optically inspected, then pressed with the L1, the first double - sided core board, and the L4 into the first four - layer board, the circuit pattern of the first four - layer board is formed, the circuit of the first four - layer board is etched, and the first four - layer board is optically inspected;

[0031] S022, after the second double - sided core board is cut, it is sequentially browned, drilled with laser blind holes, copper - plated, electroplated to fill the holes, circuit pattern formed, circuit etched, optically inspected, then pressed with the L5, the second double - sided core board, and the L8 into the second four - layer board, the circuit pattern of the second four - layer board is formed, the circuit of the second four - layer board is etched, and the second four - layer board is optically inspected;

[0032] S030, press the first four - layer board and the second four - layer board into an eight - layer board;

[0033] S040, drill laser blind holes, copper - plate, and electroplate to fill the holes on the eight - layer board;

[0034] S041, drill laser blind holes, mechanical through - holes, copper - plate, and electroplate to fill the holes on the eight - layer board;

[0035] S042, after electroplating to fill the holes, the eight - layer board is sequentially subjected to circuit pattern formation, circuit etching, optical inspection, solder mask and character printing, wire electro - gold plating, shaping, electrical performance testing, appearance inspection, and packaging.

[0036] It should be noted that S040 and S041 are selectively used according to requirements. The prepreg is laminated with copper foils on both the upper and lower sides to form a double-sided board, so that the prepreg does not need to fill the gaps between the etched circuits with glue, such as Figure 4 the position pointed by the internal arrow inside the chip ★, thereby making the dielectric thickness highly consistent and ensuring the stability of signal transmission. As Figure 4 shown, the structure of the PCB board from top to bottom is as follows: the L1, prepreg, the first double-sided core board (the L2, core board, the L3), prepreg, the L4, prepreg, the L5, the second double-sided core board (the L6, core board, the L7), prepreg, the L8. Among them, L1-L4 are laminated to form the first four-layer board, and L5-L8 are laminated to form the second four-layer board. This is the first lamination process. Then, the first and second four-layer boards are laminated to form the PCB finished product. This is the second lamination process.

[0037] During implementation, as Figure 5 shown, in the figure, PP is the prepreg, oz is the unit of measurement ounce (ounce), and CORE is the core board. Blind vias are provided in the L1-PP layer and filled with copper plating. Laser vias are provided in the L2-CORE layer. Blind vias are provided in the L4-PP layer and filled with copper plating. Blind vias are provided in the L5-PP layer and filled with copper plating. Laser vias are provided in the L6-CORE layer. Blind vias are provided in the L8-PP layer and filled with copper plating. And through vias are provided throughout the PCB. To achieve the early connection of the L2-L3 and L6-L7 layers and solve the interconnection requirements of the third-order HDI stacked vias.

[0038] As Figure 6 、 Figure 7 are the external view and cross-sectional view of the PCB manufactured by the present invention. It can be seen from the figure that the blind vias in the PCB achieve the interconnection between layers, and the alignment accuracy of the third-order HDI stacked vias is relatively high.

[0039] In summary, in the present invention, the signal layer is laminated with copper foils on both the upper and lower sides of the prepreg to form a double-sided board, so that the prepreg does not need to fill the gaps between the etched circuits with glue, achieving high consistency of the dielectric thickness, thereby ensuring the stability of the high-frequency and high-speed impedance signal transmission in the signal layer and solving the problem of the influence of the prepreg filling glue on the thickness uniformity of the dielectric layer due to the etching sequence. Then, the PCB is produced and processed according to the above process flow, reducing one lamination process compared with the traditional process flow, reducing the influence of high temperature and high pressure on the expansion and contraction of the PCB board material, which is of great help to improving the alignment accuracy of the stacked vias, and achieving the conduction of the third-order HDI stacked vias through this process flow, and then achieving the arbitrary conduction of the stacked vias of the multi-layer HDI. The above greatly improves the practical value of the present invention.

[0040] The embodiments described above only represent one or more implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the appended claims.

Claims

1. A 5G optical module three - order HDI high - speed PCB process, characterized in that, The signal layer is laminated into a double-sided board by attaching copper foils on both sides of a prepreg There are at least 8 layers arranged from top to bottom in the PCB, namely L1, L2, L3, L4, L5, L6, L7, L8 in sequence. The L3 and the L6 are signal layers. One core board is arranged between the L2 and the L3 to form the first double-sided core board, and another core board is arranged between the L6 and the L7 to form the second double-sided core board; Process flow: S010, the first double-sided core board and the second double-sided core board are pre-treated by laser drilling blind holes, copper deposition, and electroplating to fill the holes; S020, the L1, the first double-sided core board, and the L4 are laminated into the first four-layer board, and the L5, the second double-sided core board, and the L8 are laminated into the second four-layer board; S030, the first four-layer board and the second four-layer board are laminated into an eight-layer board.

2. A 5G optical module three - order HDI high - speed PCB process according to claim 1, characterized in that, It also includes: S021, after the first double-sided core board is cut, it is sequentially subjected to brownification, laser drilling of blind holes, copper deposition, electroplating to fill the holes, circuit pattern, circuit etching, optical inspection, and then laminated with the L1, the first double-sided core board, and the L4 to form the first four-layer board. The circuit pattern of the first four-layer board is carried out, the circuit etching of the first four-layer board is carried out, and the optical inspection of the first four-layer board is carried out; S022, after the second double-sided core board is cut, it is sequentially subjected to brownification, laser drilling of blind holes, copper deposition, electroplating to fill the holes, circuit pattern, circuit etching, optical inspection, and then laminated with the L5, the second double-sided core board, and the L8 to form the second four-layer board. The circuit pattern of the second four-layer board is carried out, the circuit etching of the second four-layer board is carried out, and the optical inspection of the second four-layer board is carried out.

3. A 5G optical module three - order HDI high - speed PCB process according to claim 1, characterized in that, It also includes: S040, the eight-layer board is subjected to laser drilling of blind holes, copper deposition, and electroplating to fill the holes.

4. A 5G optical module third-order HDI high-speed PCB process according to claim 1, characterized in that, It also includes: S041, the eight-layer board is subjected to laser drilling of blind holes, mechanical drilling of through holes, copper deposition, and electroplating to fill the holes.

5. A 5G optical module third-order HDI high-speed PCB process according to claim 3 or 4, characterized in that It also includes: S042, after electroplating to fill the holes, the eight-layer board is sequentially subjected to circuit pattern, circuit etching, optical inspection, solder mask printing, wire electroplating with gold, shaping, electrical testing, appearance inspection, and packaging.

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